update openpower summit 2021 page

Signed-off-by: Toshaan Bharvani <toshaan@vantosh.com>

content/events/openpowersummit21.md

@@ -1,12 +1,12 @@
 ---
 title: "OpenPOWER Summit Virtual 2021"
-eventdate: 2021-11-04
+eventdate: 2021-10-28
 eventlocation: "Virtual"
 date: 2021-05-30
 draft: false
 ---
 
-The __OpenPOWER Summit 2021__ is going to be _virtual_ again, and will be held on __4th November 2021__.  
+The __OpenPOWER Summit 2021__ is going to be _virtual_ again, and will be held on __28th October 2021__.  
 
 The event will bring open hardware and software developers, OpenPOWER Member companies,
 researchers and academics across the ecosystem to share learnings, highlight innovation and
@@ -17,3 +17,4 @@ We are looking for presentations about OpenPOWER, more can be found on the follo
 
 We will be opening registration soon, please keep an eye on this page for updates.  
 
+{{< prereg organizer="summit" event="2021"  >}}